Clear Lake - The Largest Lake
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This should be a family friendly, educational Earthcache. There is no physical container at this location!
You should be able to answer all questions from your car or on foot.
Today, we will be learning about the Geological history of the largest natural freshwater lake in California as well as how a unique lake like this can form.
Please be respectful of the area and it's residents, big or small!
If you're on foot, please watch for cars! If you have your kids, keep them close!
Clear Lake
Clear Lake is the largest freshwater lake in California with a surface area of 68 square miles. Lakes have existed in this area for at least 2.5 million years and is possibly the oldest lake in all of North America. It's known as the "Bass Capital of the West," Clear Lake supports large populations of bass, crappie, bluegill, carp and catfish. Two-thirds of the fish caught in Clear Lake are largemouth bass, with a record of 17.52 pounds. Known as the "Bass Capital of the West," Clear Lake supports large populations of bass, crappie, bluegill, carp and catfish. Two-thirds of the fish caught in Clear Lake are largemouth bass, with a record of 17.52 pounds. Clear Lake was most recently ranked by Bassmaster Magazine in its 2016 top-100 ranking as the No. 3 best bass lake in the United States and the No. 1 best bass lake on the West Coast.
Geology of Clear Lake
Clear Lake is 19 miles by 8 miles at its widest point. The average depth is 27 ft and the maximum depth is 60 ft. The lake is situated 1,330 feet above sea level. Clear Lake is believed to be one of the oldest lakes in North America, due to a geological fluke. The lake sits on a huge block of stone which slowly tilts in the northern direction at the same rate as the lake fills in with sediment, thus keeping the water at about the same depth. Core samples of the lake's sediments, taken by U.S. Geological Survey geologists in 1973 and 1980, indicate that the lake is at least 480,000 years old. The sedimentary history of Clear Lake is unbroken. The geology of Clear Lake is described as chaotic, with numerous small faults being present in the south end of the lake as well as many volcanoes, ranging in age from 10,000 to 2.1 million years, the largest being Mount Konocti, sitting at the middle of the lake's south shore. Clear Lake is the also the largest lake completely inside the borders of California.
How Clear Lake Was Formed
The Clear Lake basin was created primarily from the stresses of the San Andreas Fault System, the eruption and subsidence of the Clear Lake Volcanics, and the erosion and deposition of the parent rock. The east-west extension of the fault system and vertical movements of the faults created and maintained the basin. Downward vertical movement within the basin created by these processes is at a rate approximately equal to the average sedimentation rate of 1/25 inch/year in the lake basin. Because these rates are essentially equal, a shallow lake has existed in the upper basin for at least the last 475,000 years. If sedimentation rates were significantly different from the downshift, then either a deepwater lake or a valley would have resulted. Although the lake has changed shape significantly over this period, it has generally been located in the same area as the existing Upper Arm.
The Clear Lake Volcanics
The Clear Lake Volcanics are the northernmost and youngest of several volcanic fields in the California Coast Ranges that are progressively older to the south. They date from 2.1 Ma to about 10 ka and have an estimated erupted volume of 100 km3. Silicic lavas are the dominant type and basalts are rare. The most voluminous rock type in the volcanic field is rhyodacite. No ash-flow tuffs have been recognized. Volcanism has moved progressively northward within the volcanic field following an early phase when predominantly basaltic andesite lava erupted over a wide area. Since about 1 Ma, volcanism has been localized south and east of Clear Lake, a long-lived lake that occupies a volcano-tectonic basin.
Definition of a Lake and Different Types of Lakes
A lake is defined as a large body of water surrounded by land.
Different types of lakes include:
Tectonic lake: Owing to the internal force action of the earth's crust, there produce the tectonic lake basins, which store water and transform into tectonic lakes.
Artificial lake: A lake created by flooding land behind a dam, called an impoundment or reservoir, by deliberate human excavation, or by the flooding of an excavation incident to a mineral-extraction operation such as an open pit mine or quarry.
Rift lake: A lake which forms as a result of subsidence along a geological fault in the Earth's tectonic plates.
Ephemeral lake: A seasonal lake that exists as a body of water during part of the year.
LOGGING REQUIREMENTS:
Please answer the following questions, to your best ability, using the information above. When you feel you have them answered correctly, send me your answers via the Geocaching websites messaging feature, or through email. Any "Found It" logs without the requirements being sent in, will be deleted.
Please include the GC code of this cache and the number of people in your party in your message.
1) From the posted coordinates, estimate the distance between where you are and the shore directly across the lake. Would it be a long swim?
2) What type of lake do you think Clear Lake is?
3) How deep do you think the water right near the posted coordinates is?
4) This is NOT a requirement. Pictures are no longer allowed to be used as a logging requirement, however, they are always encouraged! Snap a few if you'd like!
Sources: Wikipedia, USGS.gov, lake.ca.us, Personal knowledge of Geology and Earth Science.
Congrats to Firecarp for the FTF!
CAA4JN
Additional Hints
(Decrypt)
[Read the above info for the best chance at answering the logging requirements! Answers must be sent to me via the Geocaching website.]